October 7, 2008
The Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
When Mariner 10 flew past Mercury three times in 1974 and 1975, the probe imaged less than half the planet. In January, during MESSENGER's first flyby, its cameras returned images of about 20 percent of the planet's surface missed by Mariner 10. Yesterday, at 4:40 am EDT, MESSENGER successfully completed its second flyby of Mercury, and its cameras captured more than 1,200 high-resolution and color images of the planet — unveiling another 30 percent of Mercury's surface that had never before been seen by spacecraft.
"The MESSENGER team is extremely pleased by the superb performance of the spacecraft and the payload," said MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "We are now on the correct trajectory for eventual insertion into orbit around Mercury, and all of our instruments returned data as planned from the side of the planet opposite to the one we viewed during our first flyby. When these data have been digested and compared, we will have a global perspective of Mercury for the first time."
Today, at about 1:50 a.m. EDT, MESENGER turned to Earth and began transmitting data gathered during its second Mercury encounter. This spectacular image — one of the first to be returned — was snapped by the Wide Angle Camera (WAC), part of the Mercury Dual Imaging System (MDIS) instrument, about 90 minutes after MESSENGER's closest approach to Mercury, when the spacecraft was at a distance of about 27,000 kilometers (about 17,000 miles).
The bright crater just south of the center of the image is Kuiper, identified on images from the Mariner 10 mission in the 1970s. For most of the terrain east of Kuiper, toward the edge of the planet, the departing images are the first spacecraft views of that portion of Mercury's surface. A striking characteristic of this newly imaged area is the large pattern of rays that extend from the northern region of Mercury to regions south of Kuiper.
This WAC image is one in a sequence of 55: a five-frame mosaic with each frame in the mosaic acquired in all 11 of the WAC filters. This portion of Mercury's surface was previously imaged under different lighting conditions by Mariner 10, but this new MESSENGER image mosaic is the highest-resolution color imaging ever acquired of any portion of Mercury's surface.
Additionally, some of the images in this mosaic overlap with flyby data acquired by the Mercury Atmospheric and Surface Composition Spectrometer and Mercury Laser Altimeter instruments, resulting in the first time that these three instruments have gathered data of the same area of Mercury. The combination of these three datasets will enable unprecedented studies of this region of Mercury's surface.
This image, acquired about 89 minutes before the craft's closest approach to Mercury, resembles the optical navigation images taken leading up to the flyby. The resolution of this image is somewhat better than that obtained by the final optical navigation image set, and the surface visible is newly imaged terrain that was not previously seen by either Mariner 10 or during MESSENGER's first flyby.
However, the added resolution is not the main scientific advancement that will be provided by this image. This WAC image is one of 11 viewed through different narrow-band color filters, the set of which will enable detailed color studies of this newly imaged area. In addition, the Narrow Angle Camera (NAC) acquired a high-resolution mosaic of most of this thin crescent view of Mercury at a resolution better than 0.5 kilometers/pixel (0.3 miles/pixel) that will enable the MESSENGER team to explore this newly imaged region of Mercury's surface in more detail.
About 58 minutes before MESSENGER's closest approach to Mercury, the NAC captured this close-up image of a portion of Mercury's surface imaged by spacecraft for the first time. It is one of 44 in a high-resolution NAC mosaic taken of the approaching crescent-shaped Mercury, as seen at lower resolution in the optical navigation images and the approach WAC color image set.
As the MESSENGER team is busy examining this newly obtained view, data from the flyby continue to stream down to Earth, including higher resolution close-up images of this previously unseen terrain. Collectively, these images and measurements made by other MESSENGER instruments will soon provide a broad range of information for understanding the formation and geologic history of the innermost planet.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
The Applied Physics Laboratory, a division of The Johns Hopkins University, meets critical national challenges through the innovative application of science and technology. For more information, visit www.jhuapl.edu.